1. Field of the Invention
The present invention relates in general to a marine engine, and more particularly to an insulator for a charge former of the engine.
2. Description of Related Art
Conventional internal combustion engines, which power an outboard drive, typically include at least one charge former to produce a fuel charge which is delivered to the combustion chambers of the engine through an intake manifold. The charge former commonly is directly connected to the intake manifold of a cylinder head to reduce the length of the induction passage.
Many types of charge formers are sensitive to heat in that if the charge former becomes highly heated, the fuel within the charge former boils and vaporizes. As a result, the charge former does not produce a fuel charge containing the proper air/fuel mixture.
A direct mechanical connection between the charge former and the intake manifold provides a thermal conductive pathway between these components. Heat from the highly heated intake manifold easily conducts to the charge former through the direct mechanical connection and heats the fuel.
To combat this problem, prior engine designs have placed an insulator between the charge former and the cylinder head to insulate the charge former from such conductive heat. With prior insulators, however, the charge former and the intake manifold must still be bolted together. This direction connection, however, in itself forms a thermal conductive pathway between the intake manifold and the charge former, which by-passes the insulator. Although the insulator impedes to some extent conductive heat transfer between the intake manifold and charge former, the insulator does not completely isolate the charge former from such conductive heat.
Many engine designs also employ a plurality of charge formers which are linked together by one or more linkage systems. These charge formers commonly are directly connected to a common mounting flange of an intake manifold.
Because prior linkages typically expand at a different expansion rate than the intake manifold, thermal expansion of the intake manifold tends to warp the linkages. As the intake manifold expands with increased temperature, the charge formers move and the distance between the charge forms changes. The movements between the charge formers of course affects the linkages.
In the case of a throttle linkage, which interconnects a plurality of throttle valves of the charge formers, such warpage of the throttle linkage commonly varies the position of one or more of the throttle valves. The throttle valves thus become unsynchronized and engine revolution becomes unstabilized.